In general, an image-formable range for a recording medium (such as paper sheet and plastic sheet) in an image forming apparatus is defined in a specification in accordance with the size of the recording medium. The image forming apparatus also has a range mechanically capable of image formation, other than the image-formable range defined in a specification. Particularly, the structural image-formable range in a main scanning direction is decided according to, for example, a scanning range of a laser for an electrophotographic laser printer and a scanning range of an inkjet head for an inkjet printer. An image-formable range defined in a specification is generally the same among products of the same kind, while a structural image-formable range varies for each product due to such as displacement of assembling positions of parts even among products of the same kind. The structural image-formable range is typically designed so as to be larger than a maximum image-formable range defined in a specification, since an image loss occurs in the image formed on a recording medium when this structural image-formable range does not include the maximum image-formable range defined in a specification.
However, designing an apparatus so that the structural image-formable range becomes sufficiently larger than the maximum image-formable range defined in a specification causes enlargement of parts as well as cost increase. On the contrary, when the structural image-formable range is made smaller, the possibility of generating image loss increases as mentioned above. In order to counter the generation of image loss, a strategy such as conducting the part assembly process in high accuracy needs to be prepared, resulting in a cost increase.